A friend of ours once told us that
he didn’t need to study logic because he was going
to read books written by great men. He thought he would absorb good
logic by osmosis. Wouldn’t it be nice if everyone around us
was logical, especially the people we trusted?

Unfortunately, it isn’t that easy. Sometimes even people
we respect will use bad logic to support their argument. In this
article, we are going to discuss what a fallacy is and how fallacies
are committed by everybody, including the people we agree with.
First, what is a fallacy?

Recently,
this discussion took place at our house:

Little Sister: “Do you think angels
in heaven sing gospel music? They did in the VeggieTalestm movie.”

Big Brother: “I don’t think so.”

Little Sister: “I think they must.
After all, you can’t prove they don’t.”

We were astounded. Our little sister was using bad logic?
(Actually, we weren’t surprised. This sort of thing happens
all the time.) Can you tell what is wrong with this reasoning? You
see, just because we can’t prove that something doesn’t
exist does not mean that it does exist. For example,
we can’t say there is life on Mars just because nobody has
yet proven there isn’t life on Mars. That would be bad logic.
That would be a fallacy.

A fallacy is an error in logic – a place where someone has
made a mistake in his thinking. In our last article we talked about
propaganda techniques, and how to recognize techniques such as transfer.
We described how propaganda tries to manipulate our emotions to
influence us to buy something. Fallacies are another important part
of logic. Here is another example:

Mother: “I thought I told you to clean
your room.”

Calvin, waving his arms: “I did! But
giant beetles from the planet Zorg came in the window and ransacked
the place! I’m lucky to be alive!”

Mother: “That’s ridiculous.”

Calvin: “You can’t say that.
You didn’t see them. How do you know they weren’t here?”

The fallacy used in these last two examples is called proof
by lack of evidence. Proof by lack of evidence is committed
when someone claims something is true simply because nobody has
yet given any evidence that it isn’t true. People use a logical
fallacy like this when they don’t have anything better to
support their argument.

In the United States, our courts consider you innocent until proven
guilty. But, in medieval times if you were accused of a crime, the
law officers assumed you were guilty until proven innocent.

Master Torturer: “You’re a thief.
You stole the Queen’s pet pig and had him for supper. You
must have done it; you can’t prove that you didn’t do
it. Confess!”

Accused: “Ha, you did it – you
just committed a fallacy! I learned all about it in an article by
the Bluedorn boys.”

We should be glad that our laws insure that we can’t be
convicted just because there is no evidence that we didn’t
commit a crime.

The Greek philosopher Aristotle was the first to name logical
fallacies. Since his time, logicians have labeled many common errors
in reasoning. Some of these labels have cool names. The fallacy
of proof by lack of evidence is also called argumentum ad ingnoratiam.
You can tell your friends that they are using a fallacy, and then
you can give them some antiquated Latin name for it. They’ll
be impressed.

Actually, if you did that, you would be using another type of
fallacy:

We call this the fallacy of using big words, but sophisticated
people with larger vocabularies call it ad magnum verbum.
This fallacy is committed when someone uses technical jargon or
unnecessarily difficult terminology to impress or confuse someone.
Believe it or not, we have heard homeschoolers use this fallacy
when they try to impress their less “classical” friends.
Yes, homeschoolers can use bad logic too!

That brings us to the second point of our article. Everyone uses
fallacies, even people we respect.

My People Are Logical, Their People Are Not

This may come as another shock to you, but fallacies aren’t
committed only by people we disagree with (like that talk show host
you don’t like). They are also committed by people we agree
with and respect.

Jenny: “Did you hear what Candidate
A said?”

Bert: “Don’t tell me.”

Jenny: “He said his opponent is in
favor of new gun laws. Any new law will take away even more of our
second amendment rights. He says if that happens it will not be
long before the United States becomes a third world dictatorship!’”

Bert: “Sounds true to me. I like Candidate
A. He stands up for my rights.”

Jenny: “Are you kidding! He was using
the slippery slope fallacy!”

The slippery slope fallacy is when someone exaggerates
the consequences of something by asserting that one thing will necessarily
cause another thing, which will cause an even worse thing, and so
on down the slippery slope. This is a fallacy because it makes people
react out of fear that something bad will happen when, in fact,
the speaker hasn’t shown how the first thing will lead to
this cascade of evils.

Even politicians we agree with can use bad logic to support their
policies. Passing new gun laws will not necessarily mean that the
United States will become a third world dictatorship.

Letter to the Editor: “I’m outraged
that our city is going to put fluoride in our water to make us healthier.
Since when does the government have the right to decide what is
best for us! What’s next? Will they start adding Vitamin C
to our water? Before you know it, they’ll have government
approved menus and throw mothers in prison if they don’t serve
vegetables with every meal!”

This person cannot simply assert that putting fluoride in the
water will lead to having government approved menus. She must prove
that it is a fact.

Hysterical mother to her husband: “You’ve
got to teach the boys logic! If you don’t teach them logic,
they won’t learn how to think! They’ll become atheists
and die in prison! Don’t you care about your sons?”

There is no excuse for using a fallacy in logic, even if it supports
a good cause like learning logic. This mother does not know for
certain that her sons will die in prison if her husband does not
teach them logic. This unhappy chain of events may not take place.
After all, her sons may never learn logic and be elected to some
political office instead!

As you can see, it isn’t enough to notice when someone else
is using bad logic. Logic is about learning to recognize fallacies
in our own thinking as well.

Mother: “Hans, do you and Nathan have
your article for Homeschooling Today done?”

Hans: “Depends on what you mean by
done.”

Even dutiful sons like us can use fallacies. This fallacy is called
avoiding the question. It is a very common one.